Method for molding a composite article by using mold

ABSTRACT

A mold for molding a composite article has an upper half mold, a lower half mold having a base and a core mounted on the base, and a pressure plate. A plurality of holes are formed in the upper surface of the pressure plate, and springs are placed in the holes. A laminated sheet formed by laminating woven fabrics is placed on the core, and the pressure plate is put on the laminated sheet so as to press a part of the laminated sheet against the core by its weight without creasing the part of the laminated sheet. When joined to the lower mold, the upper mold compresses the springs to compress the part of the laminated sheet firmly between the pressure plate and the core, and then bends the laminated sheet along the side surfaces of the core so that the laminated sheet is shaped in a predetermined shape.

This application is a division of U.S. application Ser. No. 09/063,353filed Apr. 21, 1998, now U.S. Pat. No. 6,846,122.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mold employed in a composite articlemolding apparatus for molding a composite article, such as afiber-reinforced plastic article, by a resin transfer molding method(RTM method) which places a woven fabrics in a mold, injects a resininto the mold, and heats the resin for hardening.

2. Description of the Related Art

Various composite articles have become used in all industries includingthe aircraft industry and the automobile industry in recent years anddemand for composite articles is progressively increasing. On the otherhand, high manufacturing costs of composite articles are a seriousproblem obstructing the widespread use of composite articles. Activeresearch and development activities have been made for the reduction ofthe manufacturing costs of composite articles, and a RTM method has comeinto wide use in recent years.

A composite article molding method disclosed in JP-B No. 5-14834 bends aprepreg sheet formed by impregnating a woven fabrics with a resin toproduce a composite article. FIG. 7 shows a mold employed in a knowncomposite article molding apparatus which bends a flat woven fabrics toproduce a composite article by the RTM method. As shown in FIG. 7, themold consists of a lower half mold 80 and an upper half mold 100. Thelower half mold 80 is formed by placing a core 82 on a base 81. A wovenfabrics 90 not impregnated with a resin is placed on the core 82, andthe upper half mold 100 is joined to the lower half mold 80 to bend thewoven fabrics 90 in the shape of a channel. Then, a resin is injectedinto the mold, and the resin is heated for hardening to obtain acomposite article, namely, a fiber-reinforced plastic article.

In producing the composite article by bending the woven fabrics 90impregnated with the resin by the RTM method using the known mold shownin FIG. 7, when the upper half mold 100 is joined to the lower half mold80, the upper half mold 100 bends the woven fabrics 90 so as to followthe shape of the core 82 , and compresses the woven fabrics 90 so thatthe original thickness T(1) of the woven fabrics 90 is reduced to apredetermined thickness T(2). As shown in FIG. 8, flange parts 91 of thewoven fabrics 90 are compressed between the upper half mold 100 and thecore 82 before the upper wall 101 of the upper half mold 100 comes intocontact with a web part 92 of the woven fabrics 90. Therefore the wovenfabrics 90 is unable to slide along the side surfaces of the core 82when the upper half mold 100 is further lowered to compress the web part92 of the woven fabrics 90 so that its thickness T(1) is reduced to thethickness T(2). Consequently, the web part 92 is creased, the strengthof the composite article is reduced or the web part 92 cannot be formedin the predetermined thickness T(2).

SUMMARY OF THE INVENTION

The present invention has been made to solve such a problem in the priorart and it is therefore an object of the present invention to provide amold for a composite article molding apparatus, capable of molding afiber-reinforced plastic article of a satisfactory quality not havingany creases by the RTM method.

According to the invention, a mold for molding a composite articlecomprising a lower half mold having a base and a core mounted on thebase a pressure plate placed on a laminated woven fabrics mounted on thecore of the lower half mold, having elastic means on an upper surface ofthe pressure plate for pressing the laminated woven fabrics against thecore; and an upper half mold capable of shaping the laminated wovenfabrics into a predetermined shape in cooperation with the core of thelower half mold and the pressure plate by compressing the elastic meansof the pressure plate to compress the laminated woven fabrics betweenthe pressure plate and the core of the lower half mold.

According to the one feature of the invention, the elastic meanscomprises a plurality of elastic members arranged on the upper surfaceof the pressure plate.

According to the another feature of the invention, the elastic meansincludes a spring.

According to the another feature of the invention, the elastic meansincludes a hole formed in the upper surface of the pressure plate, aguide pin set upright at a center of a bottom surface of the hole, and aspring placed in the hole and surrounding the guide pin; and the upperhalf mold is provided with a recess in a portion corresponding to theguide pin to receive the guide pin therein.

According to the another feature of the invention, the upper half moldcomprises an outer section and an inner section divided from the outersection through a dividing interface; and the inner section is dividedabove the pressure plate.

According to the another feature of the invention, the core has sidesurfaces perpendicular to an upper surface of the base, and the innersection of the upper half mold has an inner surface perpendicular to theupper surface of the base and corresponding to the side surfaces of thecore, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description takenin connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a mold in a first embodiment accordingto the present invention;

FIG. 2 is a cross-sectional view of the mold shown in FIG. 1;

FIG. 3 is a cross-sectional view of the mold shown in FIG. 1 in a closedstate;

FIG. 4 is a longitudinal sectional view of the mold shown in FIG. 1 in aclosed state;

FIG. 5 is a perspective view of a composite article molding apparatusemploying the mold in the first embodiment;

FIG. 6 is a cross-sectional view of a mold in a second embodimentaccording to the present invention in a closed state;

FIG. 7 is a cross-sectional view of a mold employed in a prior artcomposite article molding apparatus; and

FIG. 8 is a cross-sectional view of the mold shown in FIG. 7 in amolding process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a mold in a first embodiment according to thepresent invention comprises a lower half mold 10, a pressure plate 40and an upper half mold 50. As shown in FIG. 2, the lower half mold 10has a base 13 having the shape of a flat plate, and a core 20 having ashape corresponding to the shape of a composite article to be molded andmounted on the base 13. An endless groove 11 is formed in the uppersurface of the base 13 so as to surround the core 20, and a sealingmember 12 of silicone rubber is fitted in the groove 11.

The pressure plate 40 to be placed on a laminated sheet 30 laminatedwoven fabrics not impregnated with a resin, which is formed bylaminating woven fabrics, is provided in its upper surface with aplurality of holes 41 in a longitudinal arrangement as shown in FIG. 1.Circular grooves 42 are formed in the upper surface of the pressureplate 40 so as to surround the holes 41 and 0 rings 43 are fitted in thegrooves 42, respectively. The pressure plate 40 is made of a metalhaving a large specific gravity and having a small coefficient ofthermal expansion, such as a steel. A guide pin 45 is set upright at thecenter of the bottom surface of each hole 41, and a spring 44 is placedin the hole 41 and surrounding the guide pin 45. The spring 44 has alength greater than the depth of the hole 41 and projects upward fromthe upper surface of the pressure plate 40 in a free state. In thisembodiment, the width of the lower surface 46 of the pressure plate 40is substantially equal to the width of the flat upper surface of thecore 20. The widthwise corners of the lower surface 46 of the pressureplate 40 may be rounded and may be extended to positions correspondingto the rounded edges of the core 20.

The upper half mold 50 has a substantially U-shaped cross section, andhas an upper wall 51, opposite side walls 53, and flanges 54respectively extending from the lower ends of the side walls 53. Whenthe mold is closed, the inner surface of the upper wall 51 of the upperhalf mold 50 comes into close contact with the upper surface of thepressure plate 40. Recesses 52 are formed in the lower surface of theupper wall 51 at positions respectively corresponding to the guide pins45. The side walls 53 has inclined inner surfaces corresponding to theshape of a composite article to be molded. When the mold is closed, aspace conforming to the shape of the composite article is formed betweenthe inner surface of the upper half mold 50 and the surface of the core20 to shape the laminated sheet 30 into a predetermined shape.

The laminated sheet 30 is placed on the upper surface of the core 20,the pressure plate 40 is placed on the laminated sheet 30 to hold thelaminated sheet 30 between the core 20 and the pressure plate 40. Thelaminated sheet 30 is compressed firmly between the core 20 and thepressure plate 40 by the weight of the pressure plate 40 without beingcreased. Then, the upper half mold 50 is lowered toward the core 20 andthe pressure plate 40 to close the mold. As the upper half mold 50 islowered, the side walls 53 of the upper half mold 50 bend the laminatedsheet 30 gradually so that flange parts of the laminated sheet 30extends along the side surfaces of the core 20 to be formed into theshape of a channel. As the upper half mold 50 is lowered further, theupper wall 51 of the upper half mold 50 compresses the springs 44 tocompress a web part of the laminated sheet 30, namely, a part of thelaminated sheet 30 on the upper surface of the core 20, into apredetermined thickness by the resilience of the springs 44. Thedimensions of the upper half mold 50, the springs 44 and the pressureplate 40 are determined so that the upper wall 51 of the upper half mold50 compresses the springs 44 before the side walls 53 of the upper halfmold 50 press the flange parts of the laminated sheet 30 firmly againstthe side surfaces of the core 20. Therefore, when compressing the webpart of the laminated sheet 30 into the predetermined thickness, the webpart is able to extend toward the flange parts and hence the web part isprevented from being creased. The flange parts of the laminated sheet 30are compressed firmly against the side surfaces of the core 20 by thewedge action of the inclined inner surfaces of the side walls 53 into apredetermined thickness. The flanges 54 is brought into close contactwith the upper surface of the base 13 of the lower half mold 10 to closethe mold as shown in FIGS. 3 and 4, and then the lower half mold 10 andthe upper half mold 50 are fastened together with bolts, not shown.

As shown in FIG. 5, a resin 61 contained in a pressure cylinder 60 isinjected into the mold through a resin supply pipe 63 and an inlet portformed in the upper half mold 50 by the pressure of a high-pressure gas62. The interior of the mold is evacuated through a suction pipe 64connected to the upper half mold 50 to facilitate the spread of theresin 61 injected into the mold throughout the interior of the mold. Thesealing member 12 prevents the leakage of the resin 61 from the interiorof the mold to the outside, and the 0 rings 43 prevents the leakage ofthe resin 61 into the holes 41 (FIG. 3). After the interior of the moldhas been filled up with the resin 61, the resin 61 starts flowingoutside through the suction pipe 64. Then, the resin supply pipe 63 andthe suction pipe 64 are removed from the mold, the mold is heated at anelevated temperature in a furnace or by an outside heater to harden theresin 61. After the resin 61 has hardened, the upper half mold 50 isseparated from the lower half mold 10, the pressure plate 40 is removed,and the laminated sheet 30 impregnated with the resin 61 is trimmed tocomplete a composite article. If the mold is designed so that thethickness T (FIG. 4) of a space between the upper surface of the core 20and the lower surface of the pressure plate 40 when the mold is closedis equal to the design thickness of the web part of the compositearticle, the composite article can be formed in a desired fiber volumepercentage content Vf.

Referring to FIG. 6 showing a mold in a second embodiment according tothe present invention, the mold is a composite mold comprising a lowerhalf mold 10, a pressure plate 40, and an upper half mold 50. The lowerhalf mold 10 has a base 13 and a core 20 having side surfaces 20 asubstantially perpendicular to the upper surface of the base 13. Theupper half mold 50 is divided into an outer section 55 and inner section56, 57 through a dividing interface. The inner section is divided abovethe pressure plate 40 into two inner parts 56, 57 and the two innerparts 56, 57 can be moved horizontally. The outer section 55 has aninner surface of a shape corresponding to the shape of the outer surfaceof the inner section 56, 57 as assembled. The outer section 55 has sidewalls 58 each having an inclined inner surface. The inner surface of theupper wall of the inner section 56, 57 comes into close contact with theupper surface of the pressure plate 40. The upper wall of the innersection 56, 57 is provided in its lower surface with recesses 52corresponding to guide pins 45 attached to the pressure plate 40. Theinner surfaces of the side walls of the inner section 56, 57 are shapedperpendicularly to the upper surface of the base 13 and corresponding tothe side surfaces 20 a of the core 20. Thus, spaces for forming flangeparts substantially perpendicular to a web part are formed between theinner surfaces of the side walls of the inner section 56, 57 and theside surfaces 20 a of the core 20 to shape the laminated sheet 30 in apredetermined shape resembling to a channel. The inner parts 56, 57 arejoined into the inner section along a longitudinal interface 59 locatedat the one side of the endless grooves 42 formed in the upper surface ofthe pressure plate 40.

When impregnating the laminated sheet 30 with a resin in the mold, thelaminated sheet 30 is placed on the upper surface of the core 20, andthe pressure plate 40 is placed on the laminated sheet 30 to hold thelaminated sheet 30 in place. A web part of the laminated sheet 30 iscompressed firmly between the core 20 and the pressure plate 40 by theweight of the pressure plate 40 without being creased. Then, the innersection 56, 57 of the upper half mold 50 is placed on the base 13 so asto cover the pressure plate 40. Consequently, the laminated sheet 30 isbent in the shape of a channel along the core 20 by the inner section56, 57 so that flange parts extend along the side surfaces of the core20. At this stage, the flange parts of the laminated sheet 30 arepressed lightly against the side surfaces of the core 20 and are in athickness greater than a predetermined thickness because the innersection 56, 57 is separated by the longitudinal interface 59. While, thesprings 44 are compressed by the inner section 56 to make the pressureplate 40 press the web part of the laminated sheet 30 firmly against theupper surface of the core 20. Since the flange parts of the laminatedsheet 30 are pressed lightly against the core 20 by the inner section56, 57, the web part of the laminated sheet 30 is able to extend towardthe flange parts when the same is compressed in a predeterminedthickness without being creased. Then, the outer section 55 of the upperhalf mold 50 is fitted on the inner section 56, 57 to close the mold.The inclined side surfaces 58 of the outer section 55 engage with theinclined side surfaces 58 of the inner section 56, 57, so that the innerparts 56, 57 are pressed gradually toward the core 20 to press theflange parts of the laminated sheet 30 firmly against the core 20 by thewedge action of the outer section 55 as the outer section 55 is lowered.Thus the flange parts of the laminated sheet 30 are compressed into apredetermined thickness without being creased. Then, a resin is injectedinto the mold to impregnate the thus shaped laminated sheet 30 with theresin, the mold is heated at an elevated temperature in a furnace or byan outside heater to harden the resin, the mold is opened after theresin has hardened, and then the laminated sheet 30 thus shaped andimpregnated with the resin is removed from the mold and trimmed tocomplete a composite article by a method similar to that previouslydescribed in connection with the first embodiment.

As is apparent from the foregoing description, the mold of the inventionholds a top part of a laminated sheet in place on the core of the lowerhalf mold with the pressure plate before side parts of the laminatedsheet are pressed against the core by the upper half mold. Therefore,the laminated sheet can be compressed between the upper half mold andthe lower half mold and can be satisfactorily shaped without beingcreased.

Although the invention has been described in its preferred embodimentswith a certain degree of particularity, obviously many changes andvariations are possible therein. It is therefore to be understood thatthe present invention may be practiced otherwise than as specificallydescribed herein without departing from the scope and spirit thereof.

What is claimed is:
 1. A method for molding a composite article by usinga mold comprising a lower half mold having a base and a core mounted onsaid base, a pressure plate placed on a laminated woven fabric mountedon said core, having elastic means on an upper surface of said pressureplate for pressing a web part of said laminated woven fabric againstsaid core; and an upper half mold capable of shaping said laminatedwoven fabric into a predetermined shape in cooperation with said coreand said pressure plate by compressing said elastic means of saidpressure plate to compress said web part between said pressure plate andsaid core, said method comprising; placing said laminated woven fabricon said core with flange parts of said laminated woven fabric extendingoutwardly from said lower half mold, placing said pressure plate on saidweb part for pressing and holding said web part against said core byweight of said pressure plate, and placing said upper half mold havingside walls on said elastic means to shape said laminated woven fabricinto said predetermined shape in cooperation with said core and saidpressure plate with increasing pressure to the web part by compressingsaid elastic means before said side walls of said upper mold press saidflange parts of said laminated sheet against side surfaces of said coresuch that the web part is able to extend toward said flange parts tothereby prevent said web part from being creased.
 2. The methodaccording to claim 1, wherein placing said upper half mold on saidelastic means by fitting a guide pin of said pressure plate within ahole of said upper half mold.
 3. The method according to claim 1,further comprising: fastening a lower half mold with said upper halfmold after a flange of said upper half mold have been brought into closecontact with an upper surface of the base.
 4. The method according toclaim 3, further comprising: injecting a resin into said mold through aninlet port formed in said upper half mold to form said laminated wovenfabric impregnated with said resin; and heating said mold at an elevatedtemperature to harden said resin to complete said composite article. 5.A method for molding a composite article by using a mold comprising alower half mold having a base and a core mounted on said base, apressure plate placed on a laminated woven fabric mounted on said core,having elastic means on an upper surface of said pressure plate forpressing a web part of said laminated woven fabric against said core, anupper half mold for molding said laminated woven fabric into apredetermined shape, and a pair of inner upper half molds placed on saidpressure plate and inserted inside of said upper half mold, said elasticmeans being placed in a hole formed in an upper surface of said pressureplate and extending between said pressure plate and said pair of innerupper half molds, said method comprising; placing said laminated wovenfabric on said core with flange parts of said laminated woven fabricextending outwardly from said lower half mold, placing said pressureplate on said web part for pressing and holding said web part againstsaid core by weight of said pressure plate, placing said pair of innerupper half molds on said elastic means for increasing said pressure tosaid web part by compressing said elastic means and for compressingflange portions of said laminated woven fabric at an inclined angle withrespect to side surfaces of said core when said upper half mold isfitted on said pair of inner upper half molds, and placing said upperhalf mold on said pair of inner upper half molds for shaping saidlaminated woven fabric into said predetermined shape by compressing saidlaminated woven fabric among said pressure plate, said pair of innerupper half molds and the core.
 6. The method according to claim 5,wherein placing said pair of inner upper half molds on said elasticmeans by fitting a guide pin of said pressure plate within a hole ofsaid pair of inner upper half molds.
 7. The method according to claim 5,further comprising: fastening a lower half mold with said upper halfmold after flanges of said upper half mold have been brought into closecontact with an upper surface of said base.
 8. The method according toclaim 7, further comprising: injecting a resin into said mold through aninlet port formed in said upper half mold to form said laminated wovenfabric impregnated with said resin; and heating said mold at an elevatedtemperature to harden said resin to complete said composite article.